Anydaynow,No apologies for ramblings necessary. The only bad...

Anydaynow,
No apologies for ramblings necessary. The only bad question is the one that is not asked.
I think exposure to metals would be extremely hard to quantify and probably a poor indicator of risk factors. I think we all had soft metal pots in the 70's. That and really bad hair styles. So if that was a question that was asked in screening, we would probably all have to answer yes.
The best screening and diagnostic indicators remain mental state examination and executive function testing. That is psychological testing. (same sort of tests used to measure effectiveness of medications in dementia research).
Differential diagnosis can be achieved sometimes via brain scans that may show causation (e.g. vascular dementia)and parts of the brain that are suffering atrophy.
I hope that helps.